Electronic switch



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INVENTOR A. G. THOMAS ELECTRONIC swITcH Fiied Jan.v 18, 1945 6 'III' IIIII Z I/ 7 l VJ MW? Y M 2 m 4 7 9 Dec. 9, 1947.

Dec. 9, 1947. A G, THMAS 42,432,260

ELECTRONIC SWITCH Filed Jan. 18, 1945 3 Sheets-Sheet 5 l F ig. /2

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Patented Dec. 9, 1947 UNITED STATES PATENT OFFICE ELECTRONIC SWITCHr Albert G. Thomas, Lynchburg, Va.

Application January 18, 1945, Serial No. 573,366-

12 Claims. l

A sometimes necessary to open and close one or more circuits by electronic relays or switches rather than by mechanical switches such as knife switches, mercury switches, toggle switches, or usual types of relays of varied construction. Where very fast speed of operation or frequent making and breaking of circuits is encountered, electronic switches are highly advantageous. In the past, however, the employment of electronic switching has entailed a complexity of apparatus involving various electronic tubes, condensers, resistors, reactances or coupling coils, and the like, all connected together to achievethe desired result. A trigger circuit, for instance, has required two gaseous relay tubes, one or more condensers, and one or more impedances, in order to provide alternate switching action of two branches of a circuit.

With my improved electronic switches, it is possible to connect a simple device in circuit and have it perform. satisfactorily although it is substituted for numerous parts or devices formerly required.

An object is to provide an electronic reversing switch.

An additional Objectis to provide a simple electronic switch comprising two or more branches or electrical paths so that when onev branch conducts current, another associated branch. is made nonconducting substantially.

Another object is to provide an electronic tube with in-built impedance for producing potential drop.

A further object is to provide an electronic tube with a readily detachable associated impedance element.

Another object is the provision of electronic switches which may be, used in place of single pole, single throw switches; or double pole, double throw switches.

Further objects are to provide electronic switches having common cathodes and two or more anodes; and having common anodes and two or more cathodes.

An additional object is the provision of an electronic switch having a common cathode and a plurality of' controlled branches with separate ancdes, or with a common anode and a plurality of controlled branches with separate cathodes.

A still further object is the provision oi an electronic tube.. with. a. perforated partition and.

2, means for controlling current flow` through the perforation.

Additional objectswill be evident. in the following description.

In the drawings:

Figure 1 is a part sectional elevation of an electronic tube or switch with in-built grid. biasing impedance or resistance.v

Figure 2 is a partsectional elevation. of a device similar to that of Figure 1` but having cylindrically shaped elements.

Figure 3 is a plan view, with envelope in section, of a double branch tube which may be used for the devices shown. in Figures 1 or 2` Figure 4 is a part sectional fragmentary view of a tube with recessed,.removable, resistor or impedance element..

Figure 5 is a part sectional elevation of adouble branch electronic` tube or switch with indirectly heated cathodes and ln-built4 resistor or impedance.

Figure 6 is a part sectional elevation of a double branch tube or switch with cross channels, which may be used as a multiple switch.

Figure 7 is a part sectional elevation of an electronic single pole double throw switch.

Figure 8 is a circuit diagram showing a. modied form of the device of Figure 'l connected in a double circuit.

Figure 9 is a part sectional elevation of an eleotronic device usefull as adouble polendouble throw switch.

Figure 10 shows an elevation of another form of electronic device useful` as a double pole double throw switch.

Figure 11 is a part sectional elevation of an electronic device useful as a multi-contact switch.

Figure 12 is a part sectional elevation of a partitioned electronic tube or switch. with plural chambers and controlled openings in the partition, for various uses.

In the following description like partsy are designated by like numbers:

In Figure 1, envelope l, preferably of. glass or the like, has inner partition 2 sealed to it forming separate chambers 3 and 4 which may be evacuated or filled with argon,4 mercury vapor, or other gases at relatively low pressure, as desired. In fact one chamber 4, for instance, may be evacuated and chamber 3 may be gas filled, or vice versa, for reasons to be described.

A suitable control element for branch 4 such as grid 5 is connected with lead 6y sealed in the envelope and a control element for chamber 3 such as grid l is connectedwith lead 8 which may be sealed in partition 2 as shown. If desired, a channel may be formed in the partition for passage of lead 8 and resistor 9 which is connected between grid 'I and the parallel connected laments or cathodes IS and Il as shown. These laments could be connected in series, however. The filaments are connected with leads I2 and I3 as indicated and the larnent connections may be imbedded in the end vwalls of the envelope as shown.

Anode Iii with connected sealed-in lead I is provided for branch 3 and anode I5 with connected sealed-in lead I'I is provided for chamber ll. Usual materials may be used for thek various parts such as cathodes, leads, anodes, grids, and the like. Where the word grid is used it is intended to denote any suitable control element for alecting an electron stream,

In operation, cathode leads I2 and I3 are connected to the terminals of a suitable source of filament current such as a battery, transformer, or line. Anode` lead I5 is connected to lead I2 or I3 through a load and a source of potential such as a battery, line, or the like.

Anode lead Il is connected to lead 8 through a load and a suitable source of potential. The anodes are of course made positive with respect to leads I2 and 8. Now if lead 6 is connected to one terminal of a source of potential, the other terminal of which is connected to lead I3, then current will, in the conventional sense, pass from anode I5 through branch 4 and from cathode II through resistor 9 and out lead 8 and thence through the rest of the circuit containing anode I 5. When this happens the potential drop across resistor 9 biases connected grid 'I negatively with respect to cathode I8, to the point of cut-off, if desired, so that no current passes through cham ber 3 when current is passing through branch il. By proper choice of resistor 9 or the anode potential of chamber 3 and perhaps other factors, the amount of current in branch 3 can bear a predetermined relationship to the amount of current in branch li.

The chambers 3 and 4 may be highly evacuated or they may contain gas to increase current conduction.

As previously stated, chamber I may be evacuated and branch 3 may contain gas. Then the current in chamber l may be controlled by grid 5 at any time but a uctuating potentialshould be applied between leads I2 and I5, in order for grid 'I to regain control on account of ionizau tion. It will be seen that if grid 5 is made negative with respect to cathode II, even to the point of cut-oli, current will be conducted through chamber 3 since it is not then biased negatively by current through resistor 9. It is obvious, therefore, that this device will serve in elTect as a single pole double throw switch. The two circuits including anodes Ill and I5 are under the control of the one grid 5. This grid may be charged to the point of cut-olf or to a lesser degree depending upon the results desired.

Lead I2, instead of being connected directly to cathode I0, as shown, could be connected to resistor 9 at a suitable point so that grid I wouldk in or on wall or partition 2 between the grids and cathodes, or elsewhere, in order to prevent interference between the cathode-grid lelds or other elds. This shielding may be grounded or connected as desired.

While this device is shown primarily as a highly exible, electronic switch or relay of great adaptability and rapidity of action, it may also be used in other `manner as an oscillator or oscillators, for instance. In fact one chamber may be caused to oscillate while the other branch carries steady current or is non-conducting or both chambers may be caused to oscillate, each at a different frequency. This may be done by charging the grids independently, in elect, l. e., using lead 8 as described. In that case potentials should be applied to grid 'I of suicient magnitude to override any biasing due to resistor S, or the phasing between the branches should be adjusted to overcome interference.

-The same relay or switch essentially, is shown in Figure 2 except that the parts are shaped differently. In this case partition 2 is cylindrical and anodes Iii and I5 are similarly shaped. These elements are preferably concentric and situated as shown. Filament I0 is helical, but may be shaped otherwise and filament II may be bent or straight. These filaments are connected in parallel. Cylindrical grids 5 and 'I surround filaments II and IS) respectively and biasing resistor 9 is connected between leads 8 and I 2. The position of this resistor has been changed so that it is situated in the end wall indicated.

The connections and operation are as described in relation to Figure 1. The current passing from anode I5 to lament or cathode I I passes through resistor 8 and out lead 8 to complete the circuit. As before, the potential drop across resistor 9 biases grid 'I negatively. Grid 5 controls the operation as described previously. The cylindrically shaped elements provide greatly enlarged surfaces and greater current carrying capacity for a given volume, than the device of Figure l.

Figure 3 shows an alternate form of construction to that of Figure l or Figure 2. In this case envelope I comprises two joined cylinders which contain cylindrical anodes and grids as indicated and the laments or cathodes may be straight wires or any suitable shape. This construction also enlarges the current capacity as compared to the device of Figure 1.

The resistor, or condenser, or other part may be snapped or otherwise fastened in a recess outside the envelope as illustrated in Figure 4. Resistor 9 is snapped in place between resilient contacts IS so that the element may readily be changed when desired. Suitable leads from contacts I9 can be connected as desired.

Figure 5 shows the same general device as in Figure 1 except that heater type cathodes are used and resistor 9 is encased in chamber 20 in envelope I. The resistor may be surrounded with heat insulation material such as asbestos or the like. Filaments I and II are shown connected in series but they can be connected in parallel. Cathodes lila and I la are indirectly heated by laments Ill and II respectively. The cathodes are preferably treated with barium oxide or other material in order to provide copious electron emission. The cathodes are .shown connected but not necessarily so.

Lead 8 is connected to one end of resistor 9 which is connected to grid 1, as in Figure 1, the other end of the resistor being connected t0 cathattacco.:

@desn Illa and IIa, as; indicated. Substantially asi described previously, current iiowingthrough chamber 4' will pass; through cathodes IIa and wa and through resistor 9 and out lead 8, .thereby biasing grid 'I negatively. One or more conducting shields 21|y may be placed in or on partition 'I to separatev the grid-to-cathode fields or other elds in the two branches. This shield may be grounded if desired.

In Figure 6 envelope I 'has cross partition iiily of glass or the like and glass partitions 2a and 2h sealed to the inside of the envelope and to par tition 29, forming chambers A, B, C, and D as shown. Channels oropenings 25 and 23 in partition 29 join chambers A and B and' chambers and D respectively. Likewise, inclined channels 26 and 21 in partition 29 join chambers A and D, respectively. Grids 5 and 'I are positioned in openings 28 and 25, respectively and are connected with suitable leads 6 and Ea sealed in envelope I.. These grids could be` placed ,near the openings, on either side of partition 2e.

Grid 'la is placed near the lower end of opening 2l, although it can be situated in the opening, and is connected with lead 'Ib and sealed in envelope I and partition 2b. Similarly, grid 5a is: placed near the lower end of openingv or channel 26, although it could be in the channel', and is connected with lead b sealed in partitions '29, 2a, and envelope I'. These leads could be brought out in other manner if desired.

Anodes I4 and I5, with leads I and I?, are provided in chambers B and D, respectively and cathodes or filaments Ill and Il with leads I2` I2a and leads I3-I3a, are provided in chambers A and C, respectively. These cathodes may be connected by'conductor 2t sealed in envelope l, or snapped in an outside recess as in Figure 4. Then the cathodes may be energized in series by connecting leads I2 and I3 to a current source, or in parallel by employing leads IZ--IZa and I3-I3a. Screens 22 and 23, with connected leads sealed in envelope I, may be provided. The chambers may contain gas or they may be highly evacuated.

In operation, considering an evacuated device, if,l grids 'Ia and 5a are made negative with respect to `"cathodes IB and II, and if grids 'E and il are made positive with respect to the cathodes by connecting them to suitable potential sources or otherwise, then ow of electrons through passages 26 and 21 can be prevented and ow of electrons from cathode Hlto anode I4, through passage 25, can be induced or allowed by grid Similarly positively charged` grid-5 will induce or allow flow of electrons from cathode H to anode I5, through passage 28. 1f grids 'I and 5 are charged suflici-ently negatively then virtually all current flow through passages 2E and 28 will cease. The amount of electron ow can be controlled by the kind and degree oi charges on the grids.

Now if grids l and 5- are negatively biased to stop ow of electrons through passages or channels and 28 and ifr grids "la and 5a are made positive (or less negative) with respect to the cathodesr suiciently to allow flow of electronsthrough passages 2? and 25, respectively, then electrons from cathode it) will ow through passage 21 to anode I5 and electrons from cathode II will flow through passage 25 to anode iii. The strength of the currents can be reg-uatcd bythe charges on the grids.

This device therefore can be made to function as an electronic double pole reversing switch the currents; through which may bc regulated in bcth. direction and strength. This furnishes a highly flexible, relay or switching device for use in cir cuits generally.

The positive terminal of a common source of; potential can b el connected to anodes It` and l5 through a load for each anode, the negative terminal of the source being connected to one of the leads of the joined cathodes. In this way ields can be: established between cathode Ill' and anode L4 and between cathode I0 and anode I5 and between cathode I I and anode I5 and also between cathodea` I'I and anode I4. f

Screens or grids 22 and 23 may be used if desired, in order to help separate the electrostatic fields. These may be grounded or charged in any `desired way. Other screens may be placed at strategic points for similar purposes. The locations of the Various grids and channels can be chosen in order to prevent least counteraction or interference between various fields. The cathodes may be spread over a considerable area in order to help prevent such interference. It is obvious that the cathodes might be separate and the anodes can be joined.

The grids can be charged in any desired combinations or sequence to produce a variety of connections and effects.

In case gas is enclosed in the chambers, a plurality ofscreens can be used adjacent the grids or other elements or passages in order to minimize spilling over of ions from one channel to another.

Separate anode potential sources joined at the common terminal, may be used.

Figure shows a tube or switch substantially equivalent to that of Figure 1 except that the parallel-connected cathodes I5 and II have their leads sealed in cross partition 29a from which they project as shown. Leads I2 and I3 are led out of partition 29a and envelope I as indicated. A resistor similar to element 9 of Figure l can be included if desired. The other parts are used as previously described. This device has the advantage of large cross sectional area for each branch, relative to the construction of Figure 1.

Figure 8 shows a switch or electronic relay similar to that of Figure '7, connected in circuit, including a grid bias resistor. Anode I5 is connected to the positive terminal of battery or other potential source 3G the negative terminal ofv which is connected to lead I2 of the cathodes, through load L1 and resistor 9. Grid I is connected to the load terminal of resistor 9. Battery or' other current source 3| is connected to leads i2 and I3 and anode It is connected to the positive terminal of potential source 32 thefnegative terminal of which is connected to the cathodes through L2.

Grid' 5- may then be used to control the current through both loads since if it is biased positively ornot suliiciently negatively with respect to cathode It, current flowing through resistor 9V willv bias grid 1 negatively to the point of cut off, if desired. Then, if grid 5 is made sufliciently negative to stop flow of current through load L2, grid 'I will be positive or not sufficiently negative to proventi current flow through load L1. Anotherl resistor Sb, preferably equal to or greater than the resistance of element 9 may be included in the circuit as shown to distribute the current flow through the leads I2 and I3 proper- 1y.V This device. is equivalent to a single pole double throw switch.

Figure. 9. shows a. double pole double throw electronic switch or relay which is, in effect, the device of Figure 7 in duplicate. Partitions 2b and 29h divide the space into four chambers with the additional anodes Ma and |a, and cathodes lila and Ha, and grids la and 5a. The operation is essentially the same as before except the elements may be charged in duplicate or singly as desired.

In Figure 10 the double pole double throw electronic switch is for the same purpose as in Figure 9 except that the anodes are common to the two sides rather than the cathodes. The anodes Ill- I5 and ida-EM serve also as partitions. The two devices of Figures 9 and 10 can be used for the same purpose in some cases and for different purposes, due to the different arrangements, in others. The anodes may be connected as shown, or separate.

In Figure 11 envelope has inner somewhat radially disposed partitions 33, 34, and 35 sealed to the upper curved inner surface. These partitions are shown as stopping short of the cathode 40, but they can pass around the cathode and seal off separate chambers against the adjacent walls. In that case a portion of the cathode would be in each chamber A', B', C', and D'. Anodes 35, 3l, 38, and 39 with connected leads sealed in envelope l are provided for chambers A', B', C', and D' respectively. Grids 4|, 42, 43, and 44 are likewise provided for chambers A', B', C', and D. These grids may be staggered as shown or placed in any suitable positions. The leads to grids 4| and 44 are sealed in envelope l as may be the leads for grids 42 and 43. These latter leads are shown, however, as being sealed in partitions 33 and 35 and brought out through the envelope. One cathode is shown extended to furnish electrons for each anode, but a plurality of cathodes can be used, either connected together or independent.

In operation, the anodes are made positive with respect to cathode 4] by means of a potential source, or sources with common negative terminal. One or more devices to be controlled, such as a relay, or input circuit for an amplifier, or other means, can be connected in series with each anode and the potential source or sources. A source of current is connected to the terminals of cathode 45. Then by charging grid 4|, say, positively, and charging the other grids negatively, current conduction can be prevented in branches or chambers B', C', and D' and anode 35 alone will be effectively in circuit. Now anode 36 can be cut out of circuit by charging grid 4| suiciently negatively and anode 3l can be cut into circuit by making grid 42 positive or less negative with respect to cathode 40. Similarly, any branch can be put into ork out of circuit by charging its grid properly. The branches can be connected consecutively or in any desired order or in any desired combination. This device serves as a multiple contact switch which can be used to distribute current to various circuits and at the same time to regulate the strength of current by controlling the charges on the grids.

Screens or shields 45, 46, and 41 may be used to assist in controlling the fields. These screens may be charged or grounded, or connected to cathode.

In case gas is enclosed in envelopel it would,

for some purpo-ses, be preferable to extend partitions 33, 34, and 35 to the bottom envelope, thus forming separately sealed chambers A', B', and C with cathode 4B passing through the parg titions and entering each chamber; or a plurality of connected cathodes, one for each chamber, can be used. Again, it is apparent that a common anode and a plurality of separate cathodes can be used.

Figure 12 shows a device similar to that of Figure 10 with the addition among others of passages 48 and 49 in partition 2b, one on either side of anodes |4|5 and Ida-|511 which can be connected or separate. Grid 49a with connected lead 5|, is provided in passage 48. Similarly, grid 50 is placed in passage 49 and has lead 52 sealed in partition 2b and envelope I. Lead 5| is likewise sealed in partition 2b and envelope Partition 2b may be enlarged in thickness near its mid point to form container 2c and in conjunction with insulating cross partition 2d, two small chambers containing respectively, iilament 53 connected to anode |i-|5, grid 54, and plate 55 connected to anode Ilia-Ia; and filament 53al connected to anode ld-|511, grid 54a, and plate 55a connected to anode |4-I5. The -iilaments and grids are provided with suitable leads, not shown brought out of the envelope through partition 2b similarly to lead 5|.

In operation, if grid 49a is made negative with respect to grids l and la or with respect to laments Il and Ila which may be connected, then electrons from filament Ia will not pass through opening i8 to anode lli-l5 and electrons from lament will likewise not pass through opening 48 to reach anode |4a-|5a. If, however, in conjunction with positively charged grids and 'la grid 49a is made positive, then electrons from both cathodes and la can reach both anodes Ill-I5 and Ida-kia; or grid 49a may be made positive with respect to grid or cathode so that electrons from that cathode will pass through opening 48 to reach anode la-|511 and at the same time grid 49a can be made negative with respect to grid 'la -or cathode la so that no electrons from cathode ||a will reach anode |4|5. It is assumed here that the anodes are connected or that the anodes are biased with respect to the proper cathode. At the same time, however, grid 'la can be positively charged with respect to lament or cathode Ila so that electrons from that cathode will reach anode lila- |511 which is suitably charged.

The same considerations hold for the elements on the opposite side of anodes lf3- l5 and I4a-I5a. Grids 5, 5a, 7|, and la may be placed in any desired positions relative to openings 4S and 49 or with relation to the cathodes or anodes. A positively charged grid is, in this description, considered as a grid not suiiiciently negative to stop flow of electrons to the designated anode or electron receiver. A negatively charged grid is considered as a grid charged negatively to the point of cut-off.

Other combinations of charged elements can be employed.

If it is desired to connect anodes Iii-E5 and la-|511 for the conventional passage of current from the former to the latter, then lament 53a will be energized to emit electrons and grid 54a can be used to control the electron ow from that filament to positively biased plate 55a and connected anode Iii-l5. Conversely, if current flow is desired from anode illa-l5a to anode |4|5, then lament 53 is energized and grid 54 can be charged to control electron ow to positively biased plate 55 connected with anode Illa-|541. If current ow in both directions is desired, either intermittently or constantly, both 9 filaments can be energized `ami the electron Vflow in'both directions can be controlled or stopped altogether. By the above described means the anodes can be electrically connected and discon- 'rec'ted very Irapidly .for any desired DUTPOS@ Such as for 'conditions in which a common potential Es'o'iirce might vbe used, for switching operations, Aforlfor other circuit adaptations. .Anodes or plates 55 and 55a `may bepositively charged with relation to the proper cathodes 53 or 53a by any suitable means.

Similar electronic bridging or connecting means can be placed between cathodes ll-l la or between cathodes I-lila when it is desired to join them electrically, as for instance, in the device of Figure 1.

Openings 48 and 49 could be extended or placed near the cathodes so that electrons from one cathode could be attracted to the adjacent cathode through the openings, the flow being controlled by grids 49a and 5t. Small metal or graphite elements 56 and 56a, and 51 and 51a may be attached to cathodes Il, ila, l, and lea, respectively, in order to receive electrons from the adjacent cathodes. These elements may be of such size and so positioned that they will receive the electrons in order to prevent cathode disintegration, Either cathode may be made positive with respect to the adjacent cathode by means of a battery or other potential source or an electronic switch similar to that shown for the anodes may be used for one or both pairs of cathodes in order to connect them rapidly either positively or negatively with respect to each other.

It is apparent that this electronic device furnishes switching or relay means of exceptional simplicity, flexibility, and versatility, and can be operated at great speed.

Many variations of detail and many combinations, sub-combinations and altered arrangements of the devices described, can be readily made without departing from the principles I have disclosed.

What I claim is:

1. An electron discharge device comprising, an envelope, crossed partition means forming four chambers; and a grid, an anode, and cathode in each chamber.

2. Same as in claim 1, said cathodes being connected in pairs.

3. Same as in claim 2, said cathodes being supported by one said partition.

4. An electron discharge device comprising, an envelope, crossed partitions within said envelope forming one pair of chambers and another pair of chambers, Van anode in each said chamber, a cathode in each said chamber supported by one of said partitions, the cathodes for 4said one pair of chambers being electrically connected and the cathodes for said other pair of chambers being electrically connected and separate from the cathodes for said one pair of chambers.

5. Same as in claim 4, and including grid means for controlling electron ow in each said chamber.

6. An electron discharge device comprising, an envelope, an anode adjacent one end of said envelope, another anode adjacent the opposite end of said envelope, a partition intermediate said anodes forming two chambers within said envelope, a cathode for one said chamber supported by said partition, a cathode for the other said chamber supported by said partition, said cathodes being directly intermediate said anodes.

'7. An electron discharge device comprising, an

10 envelope, an anode adjacent one end of said envelope, another anode adjacent the opposite end of saidv envelope, a partition intermediate said anodes forming two chambers Within said envelope, and cathode means for said chambers supported by said partition `and in substantial alignment with an axis passing through said anodes and said partition.

8. An electron discharge Vdevice comprising, an envelope, an anode adjacent one end of said envelope, another anode adjacent the opposite end of said envelope, a partition intermediate said anodes forming two chambers within said envelope, cathode means for said chambers supported directly between said anodes, and a grid for each said chamber situated between said cathode means and the anode in said chamber.

9. An electron discharge device comprising, an envelope, an anode adjacent one end of said envelope, another anode adjacent the opposite end of said envelope, a partition substantially midway between said ends and forming two chambers within said envelope, cathode means supported by said partition directly between said anodes, and a grid for each said chamber situated between said cathode means and the anode associated with said grid.

l0. An electron discharge device comprising, an envelope, a first anode adjacent a rst end of said envelope, a second anode facing said rst anode and adjacent the opposite end of said envelope, a third anode adjacent said rst end, a fourth anode facing said third anode and adjacent said opposite end, partition means forming four chambers within said envelope, cathode means supported by said partition means and associated with said first and second anodes, other cathode means supported by said partition means and associated with said third and fourth anodes, and a plurality of grids to control electron flow in said chambers.

11. An electron discharge device comprising, an envelope, a i'lrst anode adjacent an end of said envelope, a second anode facing said first anode and adjacent the opposite end of said envelope, a third anode adjacent said first end, a fourth anode facing said third anode and adjacent said opposite end, partition means forming four chambers within said envelope, cathode means for said first and second anodes supported by said device directly between said anodes, other cathode means for said third and fourth anodes supported by said device directly between said third and fourth anodes, and a grid in each of said chambers for controlling electron flow therein.

l2. An electron discharge device comprising, an envelope, a first anode within said envelope, a second anode within said envelope facing said first anode, a third anode within said envelope adjacent said rst anode, a fourth anode within said envelope adjacent said second anode and facing said third anode, partition means forming four chambers Within said envelope with one of said anodes in each chamber, cathode means for said rst and second anodes supported by said device directly between said first and second anodes, other cathode means for said third and fourth anodes supported by said device directly between said third and fourth anodes, and a grid in each of a plurality of said chambers for controlling electron flow therein.

ALBERT G. THOMAS.

(References on following page) 1 l REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,592,075 Bruskin July 13, 1926 1,684,104 Mavrogenis Sept. 11, 1928 f 1,744,653 Loewe Jan. 21, 1930 Number Schleirnann-Jensen-- July 22, 1941 

